Processing of the Bacillus subtilis thrS leader mRNA is RNase E-dependent in Escherichia coli

We have recently reported that processing occurs in the untranslated leader region of several members of a family of Gram-positive genes regulated by tRNA-mediated antitermination. We showed that cleavage at this site plays an important role in the induction of Bacillus subtilis thrS gene expression, following threonine starvation, by stabilising the downstream mRNA. Here we show that, when transferred on a plasmid, processing of the B. subtilis thrS leader can occur at the same site in Escherichia coli. Cleavage at this site is dependent on the E. coli endoribonuclease E, both in vivo and in vitro, suggesting that a functional homologue of RNase E is responsible for thrS processing in B. subtilis.

[Effects of hypoxia on the morphology and proliferation of cultured pulmonary arterial smooth muscle cell]

The effects of hypoxia (2.5% O2 and/or < 1% O2) on bovine pulmonary arterial smooth muscle cell (PASM) proliferation and phenotype change were investigated using immunocytochemical analysis and H- TdR incorporation. The results showed that hypoxia initiated the change of PASM from contractile phenotype to synthetic phenotype. The synthetic phenotype smooth muscle cell was characterized by increase in endoplasmic reticulum and mitochondria, and by decrease in alpha-actin and muscle fiber at the end of 24 h hypoxia. Then the endoplasmic reticulum became dilated, the mitochondria became swollen and myelin figure appeared after 48 h hypoxic exposure. PASM 3H-TdR incorporation was decreased at the end of 6 h hypoxia (P < 0.05), then increased gradually at the end of 12 h. PASM DNA synthesis was significantly stimulated by 24 h hypoxia (P < 0.05). Flow cytometric DNA analysis revealed that hypoxia induced significant enhancement of G2/M phase of PASMs, decreased G0/G1 phase of PASMs (P < 0.001), and only increased S phase of PASMs in 12 h anoxia group (P < 0.05), but decreased S phase of PASMs from 24 h to 48 h (P < 0.001). Immunocytochemical reaction of proliferating cell nuclear antigen (PCNA) in PASM under anoxic condition was more stronger than that of normoxic PASM at 24 h. These results suggest that hypoxia may at first inhibit and then stimulate PASM proliferation and induce phenotype change, which may lead to the development of hypoxic pulmonary hypertension.

[Study on clinical anatomy of Chinese nasal cavity and paranasal sinus related to functional endoscopic sinus surgery]

The two-dimensional image makes it difficult to determine the anatomic locations during the Functional Endoscopic Sinus Surgery (FESS), which causes many complications. The nasal columella is the best mark to identify the distance to the operating sites during the FESS. In this study, we measured the distances and angles from the base of columella to each important landmark: the anterior end of the middle turbinate, the ethmoid bulla, the posterior and superior end of the uncinate process, the basal lamina, the posterior wall of the ethmoid sinus, the posterior and superior wall of the sphenoid sinus, the anterior and posterior ethmoid artery and the ostia of the frontal sinus and the maxillary sinus in 12 Chinese adult cadavers (24 sides). Then a simple method was proposed to identify where you are operating on and where is the most perilous point. We also paid attention to the thickness of bony wall of the optic nerve canal, the superior wall of the sphenoid sinus, the papyraceous lamina and the septa of the ethmoid air cells and found that the former two were much thicker than the latters. The thicker bony wall may contribute enough safety to the optic nerve and the hypophysis in FESS.

An engineered bivalent single-chain antibody fragment that increases antigen binding activity

Bivalent single chain Fv (scFv) was constructed by fusing a polypeptide extension containing one or two cysteines to the COOH-terminus of an scFv antibody fragment. The scFv protein was expressed and secreted in a recombinant Pichia pastoris system as a dimer with a C-terminal disulfide bridge, as determined by Western blot analysis under non-reducing conditions. We found that the scFv construct with one cysteine in the C-extension (scFv-1Cys) exhibited a much higher dimer/monomer ratio than the two cysteine counterpart (scFv-2Cys). Binding activity measurements performed by means of a competitive radioimmunoassay showed that scFv-1Cys exhibited specific antigen binding activity, which was almost the same as that of the parental MAb, and approximately four- and fortyfold higher than those of the control scFv monomer and scFv-2Cys.

Structure and regulation of expression of the Bacillus subtilis valyl-tRNA synthetase gene

We have sequenced the valyl-tRNA synthetase gene (valS) of Bacillus subtilis and found an open reading frame coding for a protein of 880 amino acids with a molar mass of 101,749. The predicted amino acid sequence shares strong similarity with the valyl-tRNA synthetases from Bacillus stearothermophilus, Lactobacillus casei, and Escherichia coli. Extracts of B. subtilis strains overexpressing the valS gene on a plasmid have increased valyl-tRNA aminoacylation activity. Northern analysis shows that valS is cotranscribed with the folC gene (encoding folyl-polyglutamate synthetase) lying downstream. The 300-bp 5' noncoding region of the gene contains the characteristic regulatory elements, T box, "specifier codon" (GUC), and rho-independant transcription terminator of a gene family in gram-positive bacteria that encodes many aminoacyl-tRNA synthetases and some amino acid biosynthetic enzymes and that is regulated by tRNA-mediated antitermination. We have shown that valS expression is induced by valine limitation and that the specificity of induction can be switched to threonine by changing the GUC (Val) specifier triplet to ACC (Thr). Overexpression of valS from a recombinant plasmid leads to autorepression of a valS-lacZ transcriptional fusion. Like induction by valine starvation, autoregulation of valS depends on the presence of the GUC specifier codon. Disruption of the valS gene was not lethal, suggesting the existence of a second gene, as is the case for both the thrS and the tyrS genes.

[A direct immunogold-silver staining method for diagnosing hemorrhagic fever with renal syndrome]

A direct immunogold-silver staining (D-IGSS) method with 5nm colloidal gold-labeled rabbit anti-HFRS IgG antibodies was employed to detect HFRS virus antigen in the cytoplasm of white blood cells from HFRS patients and compared with indirect immunofluorescence assay (I-IFA). The results showed as follows: 1. The positive rate (87.5%) of HFRSV antigen detected by D-IGSS was significantly higher than that (65.6%) detected by I-IFA. in the white blood cells (P<0.05); 2. With the D-IGSS method the positive rates of HFRSV antigen in white blood cells of finger and vein blood were 81.3% and 87.5% respectively (P>0.05) with no significant difference but finger blood smears is more simple. We belive the D-IGSS method can be widely used for early diagnosis of HFRS at basic-level hospitals.

[The effects of hypoxia on angiotensin II secretion by cultured pulmonary artery endothelial cells]

The alterations of paracrine function of pulmonary arterial endothelial cells (PAEC) might play an important role in the development of hypoxic artery hypertension (HPAH). To test this hypothesis, the effects of hypoxia on angiotensin II (AT II) secretion by new born bovine PAEC were investigated. AT II secretion increased significantly when PAECs were incubated under 2.5% O2 hypoxic condition for 1.5 h (P < 0.01 vs control). But it decreased from 1.5 h to 12 h incubation and increased from 12 h to 48 h incubation under 0% O2 hypoxic condition, with significance compared with control group (P < 0.01). NO donor SIN-1 inhibited but endogenous NO inhibitor L-nitro-arginine promoted AT II secretion significantly under both normorxic and hypoxic conditions. It was also found that the concentration of cyclic guanine monophosphate in PAEC decreased significantly at 24 h incubation in 0% O2. The above results suggest that changes of AT II in PAEC may participate in the development of HPAH.

The role of adhesion molecules in the recruitment of hepatic natural killer cells (pit cells) in rat liver

Previous studies showed that blood large granular lymphocytes (LGL), which possess natural killer (NK) activity, develop within rat liver sinusoids into high-density (HD) and subsequently into low-density (LD) pit cells which show an increasing level and spectrum of tumor cytotoxicity. In this study, we investigated the role of adhesion molecules, such as CD2, CD11a, CD18, and CD54 in the recruitment of pit cells to the liver. Immunostaining for electron microscopy, and two color flow cytometry showed that most pit cells expressed CD2, CD11a, CD18, and CD54. After intravenous injections into rats with anti-CD2, anti-CD11a, and anti-CD18 antibodies, the number of pit cells per square millimeter in frozen sections of liver tissue decreased. Treatment of rats with zymosan increased the number of pit cells fivefold, whereas subsequent treatment with anti-adhesion-molecule antibodies resulted in approximately 60% lower number of pit cells. Anti-CD54, supposed to block CD54 expression on sinusoidal endothelial cells, also decreased the number of pit cells. The number of blood LGL was, however, not affected by these antibodies. These results indicate that blocking of CD2, CD11a, CD18, and CD54 antigens on blood LGL and/or liver endothelium decreased the number of pit cells in the liver. These adhesion molecules therefore play an important role in the recruitment of pit cells in the liver.

Origin of floral asymmetry in Antirrhinum

Dorsoventral asymmetry in flowers is thought to have evolved many times from a radially symmetrical ancestral condition. The first gene controlling floral asymmetry, cycloidea in Antirrhinum, has been isolated. The cycloidea gene is expressed at a very early stage in dorsal regions of floral meristems, where it affects growth rate and primordium initiation. Expression continues through to later stages in dorsal primordia to affect the asymmetry, size and cell types of petals and stamens.

Construction and expression of bi-functional proteins of single-chain Fv with effector domains

We fused various polypeptide extensions to the C-termini of single chain Fv (scFv) and disulfide-stabilized Fv (dsFv) fragments to facilitate detection of bi-functional proteins or to add biological effector domains, which included the human metallothionein (HMT) motif and biotin mimetic sequence. These bi-functional proteins were expressed and secreted in a recombinant Pichia pastoris system and showed specific anti-idiotype binding activity, as determined by competitive radioimmunoassaying. However, the fusion protein constructed with dsFv- HMT, but not scFv-HMT, had lost this binding activity. The interruption of the structural conformation as a result in dsFv-HMT may be explained by the interactions between the cysteines engineered in dsFv domains and the cysteines in the HMT region.

Effect of prostatic growth factor, basic fibroblast growth factor, epidermal growth factor, and steroids on the proliferation of human fetal prostatic fibroblasts

To study the relationship between androgen metabolism and the pathogenesis of benign prostatic hypertrophy, we purified a growth factor from benign hyperplastic tissue of human prostates and assayed the proliferative responses of human fetal prostatic fibroblasts to the purified growth factor (hPGF), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), dihydrotestosterone (DHT), and estradiol (E2). Prostatic tissue extracts were fractionated using heparin-Sepharose chromatography. The fraction that eluted with 1.3-1.7 M NaCl contained the majority of mitogenic activity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS/PAGE) of the lyophilyzed active fraction showed a band at 17,000 daltons. Human prostatic fibroblasts were isolated from fetal prostate and tested for their proliferative responses to hPGF, bFGF, EGF, DHT, and E2. hPGF, as well as bFGF and EGF, did increase tritiated thymidine incorporation into the cultured fibroblasts. DHT(10(-7) M) had a significant stimulatory effect on cell growth in serum-free media after 6 days of culture. E2(10-7 M) had no effect on cell proliferation. The combination of DHT and E2 showed no synergistic effect. We conclude that our purified hPGF, bFGF, and EGF promote cell growth directly, DHT indirectly, while E2 does not. The effect of DHT appears to be mediated via the increased production and/or secretion of growth factor(s). Possibly, the bFGF-like hPGF purified from human benign hyperplastic prostatic tissue is such a mediator.

[Study on the organ weight of sudden death cases]

In order to make clear any influence on the weight of various organs particularly in case of chronic diseases, Basing on the result of analysis carried out previously, data of 4402 autopsy cases of sudden death collected from 22 Medical Schools and Hospitals in China were studied. The organ weight analysed included those of the heart, lungs, spleen, liver, kidneys, brain and pancreas. The results showed that weights of the heart, lungs, spleen, liver and pancrease in males and weights of the the heart, spleen and pancreas in females were heavier than those of the non-sudden death cases in adults. The difference between male and female organ weights were that weight of the female brain aged above 3 months old and weight of all the 7 organs measured in adult female were lighter than the male.

The independent prediction of general intelligence by elementary cognitive tasks: genetic and environmental influences

Current theories of intelligence have, in some cases, begun to include elementary cognitive tasks. Behavioral genetic studies of intelligence have not taken these theories into account. The current study includes 135 MZ and 128 DZ twin pairs from the Western Reserve Twin Project. The 11 WISC-R subtests as well as 6 elementary cognitive tasks were employed. Using a Schmid-Leiman (1957) transformation, analyses indicate a four-group factor model, supported by a second-order general factor at both phenotypic and biometric levels. Results indicate that the general factor, group factors, and specific residuals are necessary when examining additive genetic variance. Common environmental variance can be collapsed into a single general factor.

Experience in prevention of serious complications of laparoscopic cholecystectomy

OBJECTIVE

To study the causes and prevention of the complications of laparoscopic cholecystectomy (LC).

PATIENTS AND METHODS

Based on experience with 2 428 cases, the following should be paid attention to when dissecting and separating adhesions around the gallbladder and of the Calot's triangle. The best method for the prevention of mistaking the common bile duct (CBD) for the cystic duct is to find the junction of the cystic infundibulum and duct, separate the gallbladder wall along the infundibulum, and transect the cystic duct at the junction with the infundibulum. If dense adhesions around the gallbladder or of the Calot's triangle are met with, LC should be abandoned and open the cholecystectomy (OC) should be used instead. In separating the Calot's triangle, blunt dissection should be used to avoid burning the extrahepatic bile duct (EHBD), and blind hemostasis should be avoided. If the cystic artery lies in the upper part and the back of the cystic duct, the cystic duct should be dissected out, clipped and cut first, then the cystic artery be dealt with. If the cystic artery is in the front part of the pedicle of the gallbladder, the artery should be separated, clipped and cut first. Injury to the adjacent organs may be avoided by using electric coagulating hook correctly and avoiding accidental damage to the viscera, and keeping from viscera injury due to current chemotaxis in the closed cavity of the body.

RESULTS

A total of 2427 patients were cured. One patient died of frequent episodes of supraventricular tachycardia and pneumonia on the 21st day after LC.

CONCLUSION

If LC surgeons follow the above said principles of LC technique. LC is very safe for patients with benign diseases of the gallbladder.

Characterization of topoisomerase II-DNA interaction and identification of a DNA-binding domain by ultraviolet laser crosslinking

We have used ultraviolet laser crosslinking to characterize the DNA-binding properties of highly purified yeast topoisomerase II in the absence of ATP. A single 5 ns, 20 mJ pulse of 266 nm light produced optimal crosslinking to a short DNA duplex, with an efficiency of 0.25%. An equilibrium binding constant (Keq) of 1.2 +/- 0.5 x 10(8) M(-1) was determined from kinetic analysis. Topoisomerase II showed highest affinity for supercoiled DNA. Limited proteolysis of crosslinked topoisomerase II-DNA complexes showed a site of crosslinking to be within a 29-kDa fragment with Leu-681 at its amino-terminal end. This region contains the active Tyr-783 and is homologous to the amino-terminal region of the DNA-binding bacterial gyrase GyrA subunit, suggesting a conserved DNA-binding mechanism.

Transmission imaging of large attenuators using a slant hole collimator on a three-headed SPECT system

By combining conjugate views, truncation-free attenuation profiles of patients can be obtained by using slant hole collimators on three-headed SPECT systems. The alterations in reconstruction algorithms necessary for use with slant hole collimators and potential image artifacts are discussed. Based on an evaluation of the size of objects that can be imaged without truncation and the size of the overlap region in the conjugate views, a 15 degrees slant angle was determined to be optimal. Studies with a 30 degrees slant hole collimator verified the ability of slant hole transmission imaging to provide accurate, truncation-free attenuation maps of a 56 cm lateral width phantom. The center of rotation was determined to be dependent on the slant angle and radius of rotation of the slant collimator. These studies also demonstrated that the spatial resolution in the transaxial plane of the attenuation maps depends on radius of rotation of the slant hole collimator, but does not depend on the radius of rotation of an uncollimated transmission source. A multiline transmission source was investigated for use with estimating the attenuation map in Tc-99m labeled sestamibi perfusion imaging.

Structure and function of sinusoidal lining cells in the liver

The hepatic sinusoid harbors 4 different cells: endothelial cells (100, 101), Kupffer cells (96, 102, 103), fat-storing cells (34, 51, 93), and pit cells (14, 107, 108). Each cell type has its own specific morphology and functions, and no transitional stages exist between the cells. These cells have the potential to proliferate locally, either in normal or in special conditions, that is, experiments or disease. Sinusoidal cells from a functional unit together with the parenchymal cells. Isolation protocols exist for all sinusoidal cells. Endothelial cells filter the fluids, exchanged between the sinusoid and the space of Disse through fenestrae (100), which measure 175 nm in diameter and are grouped in sieve plates. Fenestrae occupy 6-8% of the surface (106). No intact basal lamina is present under these cells (100). Various factors change the number and diameter of fenestrae [pressure, alcohol, serotonin, and nicotin; for a review, see Fraser et al (32)]. These changes mainly affect the passage of lipoproteins, which contain cholesterol and vitamin A among other components. Fat-storing cells are pericytes, located in the space of Disse, with long, contractile processes, which probably influence liver (sinusoidal) blood flow. Fat-storing cells possess characteristic fat droplets, which contain a large part of the body's depot of vitamin A (91, 93). These cells play a major role in the synthesis of extracellular matrix (ECM) (34, 39-41). Strongly reduced levels of vitamin A occur in alcoholic livers developing fibrosis (56). Vitamin A deficiency transforms fat-storing cells into myofibroblast-like cells with enhanced ECM production (38). Kupffer cells accumulate in periportal areas. They specifically endocytose endotoxin (70), which activates these macrophages. Lipopolysaccharide, together with interferon gamma, belongs to the most potent activators of Kupffer cells (28). As a result of activation, these cells secrete oxygen radicals, tumor necrosis factor, interleukin 1, interleukin 6, and a series of eicosanoids (28) and become cytotoxic against tumor cells [e.g., colon carcinoma cells (19, 22, 48)]. Toxic secretory products can cause necrosis of the liver parenchyma, which constitutes a crucial factor in liver transplantation (55). Pit cells possess characteristic azurophylic granules and display a high level of spontaneous cytolytic activity against various tumor cells, identifying themselves as natural killer cells (10). The number and cytotoxicity of pit cells can be considerably enhanced with biological response modifiers, such as Zymosan or interleukin 2 (8). Pit cell proliferation occurs within the liver, but recent evidence indicates that blood large granular lymphocytes develop into pit cells in 2 steps involving high- and low-density pit cells (88). Kupffer cells control the motility, adherence, viability, and cytotoxicity of pit cells (89), whereas cytotoxicity against tumor cells is synergistically enhanced (80, 81).

Prognostic factors of early sequelae and fatal outcome of Japanese encephalitis

A clinical case control study to identify prognostic factors present at hospital admission associated with early sequelae and fatal outcome of acute Japanese encephalitis (JE) was carried out in Gusi county, Henan Province, central China from June to September 1991. A total of 70 patients with laboratory-confirmed acute JE were studied, of whom 3 cases died and 33 cases had neurological or psychiatric sequelae at the end of three months follow-up. The results showed that acute JE at younger age, with higher body temperature, high white cell count in CSF, and deep coma present at hospital admission were markers for unfavorable outcomes (sequelae or fatal). A history of the vaccination was not correlated with the early sequelae and fatal outcome of the disease. The paper suggests that early diagnosis and treatment and universal JE vaccination for all susceptible populations are keys for decreasing incidence of sequelae and fatal outcome of acute JE.

Vl-linker-Vh orientation-dependent expression of single chain Fv-containing an engineered disulfide-stabilized bond in the framework regions

Single chain Fv fragments (scFv) derived from an antibody, MAb 174H.64 (Tru-ScintRSQ kit, Biomira), were constructed in both orientations, i.e. Vh-linker-Vl and Vl-linker-Vh, but only the latter form could be expressed and secreted in the recombinant Pichia pastoris system. The secreted scFv protein showed specific anti-idiotype binding activity. Additionally, the molecular graphic modeling has been used to identify a possible site for the introduction of an interchain disulfide bond in the framework region of Fv. These Cys-modifications of the sites were done using a method of PCR-mediated mutagenesis. The engineered protein (disulfide-stabilized Fv: dsFv) was expressed and tested for its binding activity. It was found that dsFv was as active as the corresponding scFv and more stable as determined by competitive radioimmunoassay.

Coordinated mRNA expression of c-Kit with tyrosinase and TRP-1 in melanin pigmentation of normal and malignant human melanocytes and transient activation of tyrosinase by Kit/SCF-R

The proto-oncogene c-Kit encodes a membrane receptor protein with intrinsic tyrosine kinase activity. Activation of c-Kit induces cell proliferation, differentiation or migration among different cell types. The present study provides evidence that c-Kit plays an important role in the cell differentiation rather than in cell proliferation in pigment cells. We found that normal human melanocytes and a limited number of melanoma cells, e.g. WM35, WM39 and G361 cell lines, expressed the c-Kit gene together with tyrosinase and TRP-1 genes. When exposed to alpha-melanocyte stimulating hormone, these three cell lines also showed an increased tyrosinase (dopa-oxidase) activity. By incubating these cells with 20 ng/ml of stem cell factor (SCF) which is a ligand of c-Kit receptor, we found a transient increase of tyrosinase activity 2-4 h post-incubation, indicating an early response of tyrosinase activation, either by elevating tyrosinase protein expression or by tyrosinase protein modification (e.g. phosphorylation). However, Western blot analysis using anti-tyrosinase antibody suggested that there was no change of tyrosinase protein expression between SCF-treated and non-treated cells. We therefore suggest that protein modulation of tyrosinase (e.g. phosphorylation) plays an important role in c-Kit-induced melanogenesis.

Effects of methylene blue and LY83583 on neuronal nitric oxide synthase and NADPH-diaphorase

Methylene blue and 6-anilino-5,8-quinolinedione (LY83583) have often been used as 'selective' inhibitors of soluble guanylyl cyclase. We report that in in vitro assays, both these compounds were potent inhibitors of rat cerebellar nitric oxide synthase activity. Methylene blue had an apparent Ki of 2.7 microM, while for LY83583 the Ki was 15.8 microM. Furthermore, methylene blue, but not LY83583, inhibited the NADPH-diaphorase histochemical reaction associated with nitric oxide synthase. Our results indicate that many of the effects of these drugs which have been attributed to inhibition of guanylyl cyclase, may derive from their direct inhibition of nitric oxide synthase activity instead.

[Detection of replicative form of HCV RNA in peripheral blood leukocytes and its clinical significance]

Nested RT-PCR, done by using degenerated primer pair, was used to detect hepatitis C virus RNA (HCV RNA) in serum, plasma, liver and peripheral blood leukocytes (PBLC) of 30 patients with acute and chronic posttransfusion hepatitis C and 7 asymptomatic anti-HCV positive subjects. The results showed that the percentage of positive HCV RNA in PBLC, including both the plus and minus strands, in patients with chronic hepatitis C was significantly higher than that in acute hepatitis C and asymptomatic anti-HCV positive subjects (P < 0.05-0.001). All the 7 asymptomatic anti-HCV positive subjects did not have detectable minus strand of HCV RNA in their PBLC, serum or plasma. In 17 patients who had liver histologic examination, the positive rate of both strands of HCV RNA in PBLC of acute hepatitis (AH) was lower than that of chronic active hepatitis (CAH) (P < 0.05). Both strands of HCV RNA were detected in the liver of one AH and 6 CAH patients. The present data confirmed that PBLC of patients with hepatitis C were indeed infected by HCV. The longer the infection time, the more the chance of PBLC being infected by HCV. Patients with active liver disease (CAH) had usually higher positive rate of minus strands of HCV RNA in PBLC. In the serum and plasma of all the 37 cases, minus strand of HCV RNA was not detected and the positive rate of the plus strand of HCV RNA in their serum and plasma was similar. Futhermore, the positive rate of both plus and minus strands of HCV RNA in PBLC of 30 patients with chronic hepatitis C was also similar. It is suggested that HCV not only may infect PBLC, but also replicate in PBLC and that the occurrence of minus strand of HCV RNA is associated with activity of liver disease.

[Imaging diagnosis of carcinoma of the ampulla of Vater]

Ten patients with carcinoma of the ampulla of Vater were reviewed with both ultrasonography (US), CT scans (n = 10), and hypotonic double contrast duodenum examination (n = 5). Tumor was shown by US as abrupt obstruction of distal common bile duct (n = 6), a small mass well-delineated within the dilated distal common bile duct (CBD) (n = 4). The second part of duodenum was depicted clearly in CT scan without enhancement, and a small filling defect could be revealed at the inner surface in 5 cases, as well as an abrupt obstruction of distal CBD, local mass was shown in 4 cases. Enhancement of tumor manifested as local mass and/or ductal wall thickening after iv contrast administration was shown in 3 cases. One case with local lymph node enlargement (25 mm) was revealed by US as well as CT. Non-resectability is implicated by the ill-defined contour of tumor mass and/or portal vein, superior mesenteric artery and vein, but resectability cannot be excluded by displacement and distortion of these vessels with clear delineation. Detectability of lymph node smaller than 10 mm and evaluation of T, N staging are limited by imaging examination. Local filling defect and irregularity of mucous membrane of duodenum were revealed in 4 cases by hypotonic double contrast examination.

Socio-economic status and micro-environmental factors in relation to the risk of Japanese encephalitis: a case-control study

In a population-based case-control study in Southern Henan Province, central China, children suffering from Japanese encephalitis (JE) were compared with neighborhood controls matched by age and sex in terms of several social and environmental variables. Factors found by crude analysis to be associated with an increased risk of JE included lower family income, lower parental education, living in houses near the periphery of villages and poor quality of houses. When adjustment was made for confounding variables, only the association of house location within village remained of borderline significance (OR = 0.51, 95% CI = 0.15 approximately 1.03). It is suggested that the beneficial effect of higher family income and parental education was partly due to the fact that those parents might be more conscious about having their children vaccinated in the situation where there was a shortage of JE vaccine in the study area.

The number and distribution of hepatic natural killer cells (pit cells) in normal rat liver: an immunohistochemical study

Pit cells are a unique population of cells in sinusoids and peripheral blood, which can be considered natural killer (NK) cells with large granular lymphocyte (LGL) morphology. The aim of this study was to investigate the use of the monoclonal antibody (MAb) 3.2.3 as a specific marker of rat pit cells to detect their number and distribution in the liver. The number of 3.2.3-positive cells was comparable to the number of LGL in liver low-density (LD) and high-density (HD) pit cell fractions and in blood lymphocytes (P > .05). Immunoelectron microscopy showed that nearly all LGL in hepatic LD and HD and in blood fractions were 3.2.3 positive. Using MAb 3.2.3 immunoperoxidase staining, the mean number of pit cells in liver frozen sections was determined to be 13.7 +/- 1.1/mm2. The number of pit cells was similar in the different liver lobes (P > .05). Reduced nicotinamide-adenine dinucleotide (NADH) oxidase histochemical staining, to visualize a portal to central vein gradient, combined with immunostaining was used to analyze the lobular distribution of pit cells. We found that 61.3% (17.1/mm2) of pit cells were in the periportal area and 38.7% (10.8/mm2) in the central area. We conclude that MAb 3.2.3 can be used as a specific marker of rat pit cells and therefore can be used to quantify rat pit cell number in various experimental models.

Testing a model for posthospital transition of family caregivers for elderly persons

The purpose of this study was to test a model of factors influencing family caregivers' responses and health outcomes during the 2-month period following an elder's discharge from the hospital for acute episodes of chronic illness. The elder's average age was 72.3 years. The average age of caregivers, 63% of whom were spouses of the elder, was 61 years. A longitudinal design was used for this study. Data were collected from 346 elder/caregiver dyads the day before discharge and at 2 weeks and 2 months postdischarge. Structural equation analysis was used to evaluate the conceptual model. The findings suggest that the model fits the data with an overall Goodness of Fit Index of .80.

[Diagnosis and misdiagnosis of fracture of the femoral head]

164 cases of traumatic posterior dislocation of the hip, of which 26 were associated with fractures of the femoral head, about 15.9% incidence, were treated during the year from March 1982 to March 1993. According to the pipkin classification of fractures of the femoral head, 10 cases were type 1, 6 tupe 2, 2 type 3, and 8 type 4. Of the 26 cases, 24 received emergent radiography, with 22 diagnosed and 2 misdiagnosed. The other 2 cases were found prompt auto-reduction of dislocation of the femoral head, without emergent radiography. The 4 misdiagnosed cases, because of continued pain or redislocation, came back later for radiography and then were correctly diagnosed. Besides the routine anteroposterior radiograph of the hip, pelvic oblique radiography angled 45 degrees or 60 degrees, and frog-leg anteroposterior hip radiography were needed. The CT-directed pelvic oblique radiograph was found to be the most accurate determinant of the extent of fracture displacement and the presence of intrasarticular loose fragments. Among the 19 cases operated on, 16 showed excellent-good rate (50%), and among the 7 non-operated cases, of 6 showed excellent-good rate (33%). After follow up.

A two-year experience with laparoscopic cholecystectomy--a report of 1475 cases from Kunming, China

Over a 2-year period, from 12 September 1991 to 11 September 1993, laparoscopic cholecystectomy was performed on 1475 patients with benign gallbladder disease in Kunming General Hospital, Yunnan, China. Of these, 28 cases (1.9%) were converted to open surgery. Various complications were documented in 27 instances including extrahepatic bile duct injury in 4 cases (0.3%), postoperative haemorrhage requiring laparotomy in 3 cases (0.2%) and bile leak from cystic duct stump in 1 case (0.07%). There was 1 (0.07%) death in the series. The junction between the gallbladder infundibulum and the cystic duct is an important landmark which laparoscopic surgeons must identify in the course of the procedure. Because the junction remains a comparatively constant landmark, in difficult laparoscopic cholecystectomy, excessive dissection of the bile duct would be unnecessary. During dissection of the hepatic hilus, blund dissection is recommended and the blind use of cautery and haemostasis should be avoided.

Early and late pre-mRNA processing of budgerigar fledgling disease virus 1: identification of viral RNA 5' and 3' ends and internal splice junctions

Budgerigar fledgling disease virus 1 (BFDV-1) is the first avian polyomavirus to be identified, and it possesses uncommon structural and biological properties. Here we present an analysis of the processed viral RNAs in infected chicken embryo fibroblast cells. Two early and 18 late BFDV-1 mRNAs were defined according to their 5' ends and internal splice patterns. In the early region of the genome an incomplete splice reaction covering 195 nt is responsible for creating two mRNAs that could encode small t and large T antigens, which would be initiated from a hypothetical early promoter, PE. The late mRNA 5' ends define two putative promoter regions (PL1 and PL2), 111 nt apart in the BFDV-1 genome non-coding region. The overall splicing pattern of the late mRNAs is further complicated by an alternative splice reaction of intron 2 (deletion of either 64 nt in intron 2a or of 256 nt in intron 2b) and a splice removing intron 3 (870 nt), resulting in deletion of most of the VP2-VP3 coding region. The positions of the late mRNA 5' ends and the splicing pattern indicate the existence of two open reading frames, putatively encoding two pairs of agnoproteins, in the 5' region of several late mRNAs. These mRNAs appear to be bicistronic and to encode one of the agnoproteins together with one of the viral coat proteins.

[Imaging diagnosis of localized pleural mesothelioma]

Nineteen cases of localized pleural mesothelioma (benign 9, malignant 8, unclassified 2) proved by surgery and pathology were analyzed. Imaging manifestations included large mass, elliptic or spindle in shape, often lobulated and well delineated, close to pleural surface. There were calcifications or cystic changes within the mass in some cases. Of the 9 benign cases, there were pedicles of 1-8 cm in length attached to the pleural surface in 5 cases. None of the benign mesotheliomas had chest wall invasion or rib destruction. Of the 8 malignant mesothelioma 2 were peduncalated, 5 had invaded chest wall with underlying rib destruction in 4 CT has obvious advantages for the evaluation of the location and extenst of mesothelioma. Apart from invasion of the underlying rib or soft tissue. Differentiation of benign from malignant localized mesothelioma can not be made by imaging diagnosis. As malignant localized mesothelioma often recurrs after surgery, closely following-up is recommended.

The efficacy of Japanese encephalitis vaccine in Henan, China: a case-control study

A population based case-control study to evaluate Japanese encephalitis (JE) vaccine efficacy was carried out in Gusi County, Henan Province, China from June to September in 1991. This study showed that the JE vaccine had a strong protective effect. The estimate of the vaccine efficacy was 78% (95% CI = 16-94%). An unimmunized child was at 4.54 times greater risk of developing JE than were fully immunized children during the study period. The present study may have underestimated the vaccine efficacy due to evaluation based on routine vaccination which might have been affected by vaccination management and the local cold chain system.

Molecular control of melanogenesis in malignant melanoma: functional assessment of tyrosinase and lamp gene families by UV exposure and gene co-transfection, and cloning of a cDNA encoding calnexin, a possible melanogenesis "chaperone"

Melanogenesis is a cascade of events significantly controlled by regulatory genes which are associated with the melanosomal membrane. This report introduces our current research efforts dealing with (a) the gene and protein expressions of tyrosinase and Lamp (lysosome-associated membrane protein) families by human melanoma cells after repeated exposures to UV light, (b) the coordinated alterations in the expression of the Lamp family gene and its encoding product after transfection of two genes of the tyrosinase family in human melanoma cells and (c) cloning and sequencing of a Ca(2+)-binding phosphoprotein, calnexin, which could be a candidate as a chaperone for sorting and maturation of tyrosinase and Lamp family glycoproteins in melanogenesis cascade. Our UV exposure study, as well as gene transfection and antisense hybridization experiments, has clearly indicated a marked and coordinated interaction of the Lamp-1 gene with the tyrosinase and TRP-1 genes in this process. We propose that melanogenesis is controlled at least by two major gene family products, i.e., (a) the tyrosinase family of tyrosinase, TRP-1 and TRP-2, and the Lamp family of Lamp-1, Lamp-2 and Lamp-3. These two gene families probably derived from primordial melanogenesis-associated genes which are common or closely related to each other.

NMDA-dependent nitric oxide release in the hippocampus in vivo: interactions with noradrenaline

Nitric oxide appears to act as a novel intercellular messenger activating soluble guanylyl cyclase to cause an increase in cGMP in target cells. In the nervous system, NMDA receptor activation has often been shown to result in activation of NO synthase, and many of the actions of NMDA are thought to be mediated by NO. We have recently combined intracerebral microdialysis with a sensitive assay for the NO oxidation products nitrite and nitrate, to assess NO release directly in awake, freely-moving animals. In the present study, we have applied this method to the hippocampus, where we have found that local NMDA application increases NO release. This was prevented by prior administration of an NMDA receptor antagonist or a nitric oxide synthase inhibitor. These pretreatments also reduced the basal extracellular nitrite and nitrate levels, suggesting that there may be a tonic glutamate-induced NO production in the hippocampus in awake, freely-moving animals. Previous work on NMDA-induced increases in cGMP suggested a possible role for noradrenaline. We found that pretreatment with the alpha 1A antagonists WB4101 or 5-methyl-urapidil, reduced the basal levels of NO oxidation products, however, NMDA still induced an increase in extracellular NO in the presence of these alpha 1A antagonists. In contrast, prior lesion of the central noradrenergic system with DSP4 prevented the increase in hippocampal NO release seen following local NMDA application. These results indicate that in vivo microdialysis can be used to monitor NO release in the hippocampus in response to NMDA receptor activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Alphamethrin-impregnated bed nets for malaria and mosquito control in China

A community-based intervention trial was carried out to evaluate the effectiveness of alphamethrin-impregnated bed nets for control of Plasmodium vivax malaria and its vector in an area of moderate endemicity in southern Henan province, central China in 1990. Malaria incidence was significantly lower in the intervention group than in the comparison group (2.03 vs. 3.57 per 100 person-years at risk). The protective efficacy for malaria incidence was 43%. The prevalence of malaria parasitaemia among children under 10 years old in the intervention group was about one-quarter of that in the comparison group (0.93% vs. 3.25% and 0.71% vs. 1.96% after one and 4 months use of impregnated nets, respectively). Alphamethrin-impregnated bed nets had a mass killing effect on vector mosquitoes. The outdoor person-biting density of Anopheles anthropophagus and A. sinensis decreased by 70.3% and 29.3% respectively. The density of these 2 mosquito species found resting inside treated nets was close to zero. No side effect was found among users of impregnated bed nets. Impregnation with alphamethrin was more effective on polyester than on cotton netting and residual effects lasted at least one year. Use of alphamethrin is less expensive than permethrin and deltamethrin.

The protective effect of bed nets impregnated with pyrethroid insecticide and vaccination against Japanese encephalitis

A population-based case-control study to evaluate the protective effect of bed nets impregnated with pyrethroid insecticide and of vaccination against Japanese encephalitis was carried out in Gusi county, Henan province, China from June to September 1991; 50 cases and 100 matched controls were studied. Bed nets impregnated with pyrethroid insecticide greatly decreased the risk of infection among children under 10 years old, and vaccine efficacy was 78% (95% CI 16%-94%). We suggest that impregnated bed nets could be used as a quick response during outbreaks of Japanese encephalitis.

The effect of DDT spraying and bed nets impregnated with pyrethroid insecticide on the incidence of Japanese encephalitis virus infection

A retrospective investigation was conducted to evaluate the effectiveness of DDT residual indoor spraying and bed nets impregnated with pyrethroid insecticide for Japanese encephalitis control in southern Henan province, China. DDT residual indoor spraying had no effect on the incidence of Japanese encephalitis, but it was greatly reduced after the introduction of pyrethroid-impregnated bed nets. Only a small effect on outdoor biting densities of Culex tritaeniorhyncus was found, although the number of mosquitoes resting inside bed nets decreased markedly after the introduction of bed net impregnation.

Coordinated mRNA and protein expression of human LAMP-1 in induction of melanogenesis after UV-B exposure and co-transfection of human tyrosinase and TRP-1 cDNAs

In order to better understand the cascade of melanogenic events in melanocytes, this report has introduced our two recent approaches for the expression of melanogenesis/or melanosome-associated genes and encoded proteins in melanocytes (melanoma cells) after repeated exposure to UV-B and after cotransfection of two human genes, i.e., tyrosinase and tyrosinase-related protein-1 (TRP-1). Repeated exposure of UV-B (2.5-5.0 mJ/cm2) caused not only upregulation of tyrosinase and TRP-1 genes but also coordinated increase in the gene and protein synthesis expression of Lamp-1 (lysosome-associated membrane protein-1). When COS-7 kidney cells and amelanotic melanoma (C32 and SK-MEL-24) and melanotic melanoma (G361 and SK-MEL-23) cells were exposed to cotransfection of human tyrosinase and TRP-1 cDNAs, there was also an increased expression of Lamp-1 mRNA and protein along with tyrosinase activation and new melanin synthesis. Importantly, single transfectants of human tyrosinase cDNA revealed marked cellular degeneration, whereas this degeneration was not seen in single transfectants of TRP-1 cDNA or cotransfectants of human tyrosinase and TRP-1 cDNAs, indicating that TRP-1 prevented, along with Lamp-1, programmed death of melanocytes after transfection of tyrosinase gene. The coordinated expression of TRP-1 and Lamp-1 was further confirmed by antisense oligodeoxynucleotide hybridization experiment against Lamp-1 gene, showing the decreased expression of TRP-1 as identified by three different types of anti-TRP-1 monoclonal antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Cotransfection of genes encoding human tyrosinase and tyrosinase-related protein-1 prevents melanocyte death and enhances melanin pigmentation and gene expression of Lamp-1

We constructed two genes specific to melanogenesis, human tyrosinase (HT) and tyrosinase-related protein-1 (TRP-1) genes, into two separate expression vectors so that the cloned genes were under the control of a human cytomegalovirus promoter and enhancer. Monkey kidney COS-7 cells and human amelanotic and melanotic melanoma cells were then cotransfected by both HT and TRP-1 or transfected individually with each gene. The transfectants were examined for mRNA expression by reverse transcription-mediated RNA-PCR amplification. HT or TRP-1 mRNA was strongly expressed in HT or TRP-1 transfectants and cotransfectants of the two genes. Both light and electron microscopic observations indicated that degeneration and premature death of melanocytes occurred in HT transfectants, but not in TRP-1 transfectants or in HT and TRP-1 cotransfectants. Cotransfected cells from five cell lines revealed numerous granular reaction products with an anti-TRP-1 antibody and lysosomal granules with electron-dense material. Our melanin assay confirmed the new production of melanin pigments in these cells, indicating that the lysosomal granules would contain melanin pigments. The gene expression studies of lysosomal protein (beta-galactosidase, CD63, Lamp-1, and Lamp-2) revealed a dramatically elevated gene expression of Lamp-1, which is associated with the membrane receptor of lysosomal granules, in HT- and TRP-1-cotransfected cells. Conversely, the treatment of melanoma cells with antisense oligodeoxynucleotides against Lamp-1 resulted in a decreased expression of TRP-1 protein by immunoprecipitation, supporting the observations of the HT and TRP-1 cotransfection study regarding the up-regulation of Lamp-1 expression. We conclude that HT, TRP-1, and Lamp-1 gene products may function together, being expressed as a multiprotein complex within the melanosomal compartment. Specifically, HT and TRP-1 may function together via Lamp-1 by stabilizing the enzyme-protein complex within the melanosome and prevent the premature death of melanocytes due to tyrosinase-mediated cytotoxicity.

Expression and DNA binding of budgerigar fledgling disease virus large T antigen

Budgerigar fledgling disease virus (BFDV) represents the first non-mammalian member of the polyomavirus genus and possesses uncommon structural and biological properties. Recombinant baculoviruses were constructed to express BFDV small t antigen, large T antigens, as well as a large T deletion mutant Td and beta-galactosidase-Td fusion proteins to high levels in infected insect cells. A recombinant virus containing a genomic copy of the BFDV early region was used for small t antigen expression, and corresponding intron-deleted cDNAs for production of large T antigen derivatives. Recombinant T as well as authentic T antigen proteins from infected chicken embryo fibroblasts were purified using both immunoaffinity and DNA affinity column chromatography. We present evidence that the large T antigen interacts specifically with DNA sequences present in the non-coding region of BFDV; by indirect DNA immunoprecipitation mapping and DNase I footprinting, four regions including 12 DNA-binding sites have been determined that cover most of the BFDV non-coding region. The T antigen binding pattern observed suggests a protein-DNA interaction system considerably different from those of simian virus 40 and other polyomaviruses.

Inhibition of nitric oxide synthase by antineoplastic anthracyclines

Nitric oxide synthase, the enzyme responsible for the synthesis of nitric oxide and citrulline from arginine, was potently inhibited by the anthracycline antibiotics doxorubicin (Ki = 24 microM) and aclarubicin (Ki = 50 microM). These drugs were non-competitive inhibitors with respect to arginine. This action on nitric oxide synthase may explain some of the cardiovascular and cytotoxic actions of these chemotherapeutic drugs.

Metalloporphyrins inhibit nitric oxide-dependent cGMP formation in vivo

Sodium nitroprusside produced a dose-dependent increase in extracellular levels of cGMP in the cerebellar cortex in vivo. This was independent of nitric oxide synthase activity. The metalloporphyrins zinc-protoporphyrin-IX, tin-protoporphyrin-IX and zinc-deuteroporphyrin-IX,2,4-bis glycol prevented the increase in cGMP in the cerebellar cortex produced by sodium nitroprusside. At high doses, tin-protoporphyrin-IX also decreased the basal extracellular levels of cGMP. These drugs had no effect on nitric oxide synthase activity. We conclude that the neuropharmacological effects of metalloporphyrins may result from their direct inhibition of soluble guanylyl cyclase, rather than from an effect on carbon monoxide synthesis.

Role of gene expression and protein synthesis of tyrosinase, TRP-1, lamp-1, and CD63 in UVB-induced melanogenesis in human melanomas

Using melanotic cells (SK-MEL-23 and G361) and amelanotic cells (C32 and SK-MEL-24) of human melanoma, this study examined whether UV-B irradiation has a direct stimulatory effect on the expression of genes involved in melanogenesis. Our initial screening of methylthiazol tetrazolium (MTT)-formazan formation assay indicated a low dose of ultraviolet (UV)-B irradiation, 2.5 and 5.0 mJ/cm2, can metabolically stimulate these cells. Repeated exposure of UV-B at 5.0 mJ/cm2 for seven consecutive days resulted in increased tyrosinase activity and melanin synthesis in SK-MEL-23 and G361 cells, but not in C32 and SK-MEL-24 cells. On reverse-transcription-polymerase chain reaction and immunoprecipitation studies, the two melanotic cell lines exhibited upregulated expression of mRNA and antigenic epitopes of tyrosinase, tyrosinase-related protein (TRP-1; gp75/HMSA-5), and lysosomal membrane associated protein (Lamp-1). The amelanotic cell line, C32, expressed the tyrosinase gene and protein constitutively but revealed no active tyrosinase or melanin synthesis even after UV-B exposure. Another amelanotic cell line, SK-MEL-24, exhibited no expression of tyrosinase gene and protein before and after UV-B exposure and, therefore, no melanin synthesis. Both C32 and SK-MEL-24 showed no gene or protein expression of TRP-1 before or after UV exposure, but upregulation of the Lamp-1 gene and protein expressions after exposure. We conclude that tyrosinase is the key enzyme responsible for UVB-induced melanogenesis. Both TRP-1 and Lamp-1 act together in melanogenesis, TRP-1 being essential and necessary. There is no change in the expression of CD63 lysosomal membrane protein at either the mRNA or protein level.

Ribozyme mediated destruction of influenza A virus in vitro and in vivo

Short catalytic RNAs with inherent, specific endoribonuclease activity, called ribozymes, have recently been shown to exist in nature. According to the structural models artificial ribozymes have been designed that can potentially hydrolyse any chosen target RNA sequence in trans at a specific site. We have constructed and characterized in vitro hammerhead and hairpin ribozymes designed to cleave viral RNA segment 5 of influenza A virus. Both ribozymes were functional under optimal in vitro conditions, but quantitative measurements indicate that the hammerhead ribozyme is considerably more efficient at this target site than the hairpin ribozyme. Mg2+ dependent hammerhead ribozyme-mediated cleavage reactions were enhanced at higher temperature and in presence of spermidine, but catalytic activities were retained also in cellular extract S-100 or nuclear extracts at physiological temperatures. Recombinant plasmids derived from transfection vector pSV2-neo were engineered to allow the expression of specific ribozymes under the control of SV40 early promoter or SV40 early+ late promoters. These plasmids were introduced by transfection into COS cells, and their expression and enzymatic activities were analyzed in stable cell lines after selection of neomycin-resistance. Several permanent ribozyme-expressing clones were established and characterized: ribozyme coding DNA sequences and synthesis of ribozyme RNA molecules in the transfected cells were determined and monitored by polymerase chain reactions. It was found that the highest levels (up to 70-80%) of resistance to influenza A virus strain X-31 super-infection was observed in COS cells transfected with plasmids containing SV40 early or SV40 early+late promoters coinciding with relatively high and constitutive rates of ribozyme expression. These results suggest the feasibility of developing ribozymes designed against influenza virus to achieve therapeutic value.

[Laparoscopic cholecystectomy performed in 235 cases of cholecystitis with impacted gallstones]

During the past 2 years, 235 cases of cholecystitis with impacted gallstones were treated with laparoscopic technique. There were 221 chronic cases and 14 acute cases accounting altogether for 15.19% of a total of 1475 patients undergoing laparoscopic cholecystectomy during the same period. As a result, 9 of these patients were converted to open surgery. Severe adhesion around the gallbladder or/and in the Calot triangle in 7, acute impacted gallstone, gallbladder necrosis along with obscure anatomy in the calot triangle in 1, and gallstone impacted at the junction of the common hepatic and cystic duct in 1 were observed. Conversion rate was 3.8%. Postoperative bile leakage developed in 2 cases and healed spontaneously. There were no intraperitoneal sepsis and perioperative death in our patients. The diagnosis, classification, and management for acute or chronic impacted gallstone are discussed.

A comparative study usefulness of magnetic resonance imaging in the diagnosis of acute cholecystitis

The utility of magnetic resonance imaging (MRI) in the diagnosis of acute cholecystitis was evaluated in 72 consecutive individuals (5 healthy, 13 with chronic cholecystitis and silent gallbladder stones, 43 without biliary or diffuse liver disease, and 11 with acute cholecystitis and gallbladder stones) with a 0.5-T superconducting unit. On the T1-weighted (500/20) and less T1-weighted axial spin-echo images (620/25), the liver/gallbladder signal intensity ratio (mean +/- SD) was 2.5 +/- 0.51 (n = 5) and 1.8 +/- 0.29 (n = 8) in acute cholecystitis; 0.9 +/- 0.42 (n = 6) and 1.0 +/- 0.29 (n = 9) in chronic cholecystitis; and 0.9 +/- 0.14 (n = 5) and 0.8 +/- 0.19 (n = 43) in normal gallbladder, respectively. Our results indicate that the liver/gallbladder signal intensity ratio on the T1-weighted image may be a simple and reliable indicator for the diagnosis of acute cholecystitis; we suggest further investigation to confirm these results.

Plutonium-catalyzed oxidative DNA damage in the absence of significant alpha-particle decay

Plutonium is considered to be a carcinogen because it emits alpha particles that may result in the irradiation of stem cell population. In the present study we show that plutonium can also catalyze reactions that induce hydroxyl radicals in the absence of significant alpha-particle irradiation. Using the low specific activity isotope, 242Pu, experiments were performed under conditions in which chemical generation of hydroxyl radicals was expected to exceed the radiolytic generation by one hundred thousand-fold. The results showed that markers of oxidative DNA base damage, thymine glycol and 8-oxoguanine could be induced from plutonium-catalyzed reactions of hydrogen peroxide and ascorbate similarly to those occurring in the presence of iron catalysts. Plutonium-242, as a neutralized nitrate in phosphate buffer, was 4.8-fold more efficient than iron at catalyzing the oxidation of ascorbate at pH 7. The results suggest that plutonium complexes could participate in reactions at pH 7 that induce oxidative stress--a significant tumor-promoting factor in generally accepted models of carcinogenesis.

Nitric oxide-dependent efflux of cGMP in rat cerebellar cortex: an in vivo microdialysis study

The stimulation of excitatory amino acid receptors in the cerebellar cortex results in the Ca2+/calmodulin-dependent activation of nitric oxide synthase. This leads to an increase in tissue levels of cGMP following the interaction of nitric oxide with soluble guanylyl cyclase. The cerebellar cortex has the highest levels of nitric oxide synthase and cGMP in the brain; however, the levels of guanylyl cyclase and cGMP-phosphodiesterase are remarkably low. Thus, the mechanisms regulating cGMP levels in cerebellar cells are unclear. One report has noted that cGMP can be released from cerebellar slices. We have therefore used intracerebellar microdialysis in awake, freely moving rats to test the hypothesis that activation of nitric oxide synthase in the cerebellar cortex results in the release of cGMP. Climbing fibers, which release excitatory amino acids in the cerebellum, were activated with systemic harmaline. This resulted in an immediate increase in extracellular cGMP, which was blocked by TTX or the removal of extracellular Ca2+, and attenuated by prior lesion of the climbing fibers. Blockade of N-type calcium channels with omega-conotoxin also antagonized the harmaline-induced increase. In contrast, blockade of L-type calcium channels, or inhibition of anion transport with probenecid or bromosulfophthalein, potentiated the increase in cGMP seen in response to harmaline. Inhibitors of nitric oxide synthase or guanylyl cyclase prevented the harmaline-induced increase in extracellular cGMP, while phosphodiesterase inhibitors potentiated the increase. Local application of the NMDA antagonist 2-amino-5-phosphonopentanoic acid or the AMPA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione attenuated the effect of harmaline.(ABSTRACT TRUNCATED AT 250 WORDS)

N-methyl-D-aspartate-induced nitric oxide release: an in vivo microdialysis study

Increasing evidence indicates that nitric oxide acts as an intercellular signal transduction molecule in the nervous system. In particular, in vitro studies have demonstrated that nitric oxide is produced in the cerebellar cortex and is responsible for the increases in cyclic GMP seen in response to glutamate receptor activation. In this study, we have combined the technique of intracerebellar microdialysis with a sensitive assay for nitric oxide oxidation products nitrate and nitrite, to assess nitric oxide release directly in awake, freely moving animals. We have found that infusion of N-methyl-D-aspartate via the microdialysis probe results in a dose-dependent increase in cerebellar nitric oxide release. This increase was prevented by prior administration of an N-methyl-D-aspartate receptor antagonist, or the nitric oxide synthase inhibitor NG-nitroarginine. Both these pretreatments also reduced the basal extracellular nitrite and nitrate levels, suggesting that there is a tonic glutamate-induced nitric oxide production in the cerebellum of awake, freely moving animals. These results provide direct evidence for nitric oxide release in response to N-methyl-D-aspartate receptor activation in the adult cerebellar cortex, in vivo. This new approach, coupling microdialysis with the azo dye detection method of Griess, should thus prove useful for the in vivo study of nitric oxide release from various brain regions in response to pharmacological, physiological or behavioral manipulations.